This invention relates to electronically scanned antennas, and more particularly to a conformal dielectric covered continuous antenna useful in guided missiles with an infrared seeker located in the missile cone.
In one type of guided missile, a twist Cassegrain reflector antenna on gimbals is used for the RF seeker, with an IR seeker at the nose tip of the radome. The diameter of the IR seeker tends to block some of the view of the RF seeker antenna. It would therefore be an advantage to provide an antenna system with improved RF seeker performance.
One possible solution could be to use a xe2x80x9cbug eyexe2x80x9d IR seeker in order to remove the blockage problem. However, in order to see everywhere with the bug eye IR seeker, the missile would have to roll. It would further be advantageous to provide an antenna system with improved RF seeker performance and which eliminates the blockage without rolling the missile.
A dielectric covered continuous slot (DCCS) antenna operable at RF frequencies is described, in accordance with one aspect of the invention. The antenna includes a conical or cylindrical dielectric radome structure having a nominal thickness equal to one quarter wavelength at a frequency of operation of the antenna. A conductive layer is defined on a contour surface of the radome structure, with a plurality of continuous slots defined in the conductive layer. The slots extend circumferentially about the longitudinal axis of the antenna and are spaced apart in a longitudinal sense. A serpentine end-fed signal transmission structure is disposed within the radome structure for carrying RF feed signals from an excitation end of the structure to a second end of the transmission structure. The slots are disposed along the serpentine transmission structure such that energy leaks from the transmission structure through the slots and the radome structure, forming a beam which is scannable in a direction along the longitudinal antenna axis by scanning the transmit signal frequency. Due to the frequency dispersive effective electrical length of the transmission structure, the slot spacing effectively changes as the frequency is scanned, thereby scanning the beam.
This antenna provides room for an IR (infrared) seeker in the nose of the cone, without blocking the view of the conical/cylindrical antenna.
The dielectric cover of the DCCS antenna has a thickness of about one quarter wavelength, reducing the radiation from each slot to such a small amount that several slots can be cascaded as an efficient frequency scanned travelling wave antenna.